When a site or a good is protected whit a conservation status, either national or local, the municipal regulations are one of the main tools to manage the built environment modifications. How do the regulation participate in values conservation? To explore this question, we chose to study the case of the arrondissement historique et naturel du Mont-Royal (AHNMR), a major site in the Montreal identity. We listed the heritage values recognized to the site and analyzed the project management process in the four boroughs who share the Montreal part of the AHNMR territory; we analyzed a few permit requests as well. The process is complex, the evaluation being mostly discretionary, including functionary analysis and advisory comities as well as public consultation exercises. The research highlights that urban regulation tend to concentrate on values know for their materiality (architectural values, landscape values for instance) and to neglect immaterial values (custom values, identity and iconic values). The values juxtaposition can mitigate this disproportion by protecting an immaterial value through a material value. The documentation on heritage values and their embodiment in the arrangement of a site has a major importance for the application of the evaluation criteria. The discretionary evaluation brings multiple views on a project, actor’s opinions, heritage experts or non-experts, generally not participating in project’s evaluation process, which contributes to their evolution. Public consultations give rise to reevaluating heritage values as well as knowledge deepening.